I had an earlier cool pad a few years ago and it wouldn't show up either.its a metro pcs.that has been factory reset stops at the Google pre owner login. I used the keyboard work around got into phone went on web and none of the you tubes FRP were exactly helpful. It let me rename startup apk and of course it stops at the metro logo on boot now considered adb. Called metro they don't have any info on that imei #. I was only requesting old phone number because the sim I put in it was receiving calls (and with previous workaround could dial out). But no recognition from USB?
FRP locks everything. Don't expect your device to be detected while FRP is enabled! By the way, you need to enabled USB debugging in the developer options to get ADB work which is locked as well.
So just keep trying to find a suitable method to bypass the lock on your device since Google actively patchs loop hole so none of the methods found on YouTube videos works anymore.